Earthquakes in eastern Ohio have prompted stiff new regulations for some energy companies. The companies dispose of waste water from fracking by injecting it into deep underground wells. And some low-magnitude quakes in the Youngstown area have been linked to that disposal process. So Ohio's Department of Natural Resources introduced the new rules today.

NPR's Jeff Brady joins us now. And, Jeff, let's start with an explanation of this waste-water. What are we talking about?

JEFF BRADY, BYLINE: Well, I think most of us have heard of hydraulic fracturing, better known as fracking. It's that controversial practice of pumping water and chemicals and sand underground to force gas or oil out of tight rocks. And we're talking about a lot of water here, several million gallons for just one well. When that water comes back up to the surface, it's called brine, which gives you a good sense of how nasty it is. It's full of minerals and other gunk. With the drilling boom around western Pennsylvania, there's a lot of this of brine to dispose of.

Companies have been trucking it over to Ohio, where it's pumped deep, nearly 2 miles underground. Federal regulators have determined this is the best way to get rid of that stuff.

SIEGEL: And starting about a year ago, there was a series of earthquakes near Youngstown, Ohio. Tell us about that.

BRADY: Yeah. The quakes began about March of last year. There have been a dozen since then, relatively small magnitude quakes from 2.1 to 4.0, not really strong enough to cause much damage. But folks in Ohio aren't really used to earthquakes at all. So when a 4.0 quake struck on New Year's Eve just a few months back, that worried a lot of people.

SIEGEL: Well, is it clear that the earthquakes were related to injecting the brine underground?

BRADY: You know, Ohio's Department of Natural Resources doesn't say that the quakes are definitely related to a disposal well. But I talked with a U.S. Geological Survey scientist who specializes in this, and he says there's no doubt in his mind that they're related. They happened near the well after there had been a lot of waste pumped in. And now, it's also clear that there was a previously undiscovered fault line near that well.

SIEGEL: And this isn't the first time that there have been earthquakes blamed on processes related to fracking. Other states have experienced problems like this, no?

BRADY: Absolutely. Some people have connected earthquakes in places like Arkansas to disposal wells. These wells are all over the country - tens of thousands of them - and very few of them have led to any problems. But as we see more oil and gas drilling in this country, most of it involving hydraulic fracturing, these disposal wells are going to become even more important. And you can't predict everything that will happen when you pump millions of gallons of brine underground. Scientists and regulators are still learning about this process.

SIEGEL: So, Jeff, what are the new regulations that Ohio has put in place?

BRADY: Well, before any of these disposal wells are allowed, companies will have to do some extra geological work. If there's a fault line nearby, you probably won't be able to put a disposal well there. The state also says companies won't be allowed to drill very deep down into what's called the Precambrian bedrock. The thinking is if you stay above that, then there will be fewer problems. Companies also will have to electronically monitor where the brine goes, what's in it, and they'll need some sophisticated ways to monitor pressures underground to make sure nothing is going wrong.

The Ohio Department of Natural Resources in announcing these new regulations really played up that this gives the state the strictest guidelines in the country, so maybe other states will be following their lead there.